An organic electroluminescence (EL) device generally comprises an anode, a cathode, and one or more organic thin film layers sandwiched between the anode and the cathode. When a voltage is applied between the electrodes, electrons are injected from the cathode and holes are injected from the anode into a light emitting region. The injected electrons recombine with the injected holes in the light emitting region to form excited state. When the excited state returns to the ground state, the energy is released as light.
Many researches have been made on the applications of organic EL device to display, etc. because of its possibility of wide selection of emission colors by using various emitting materials in a light emitting layer. Particularly, the research on the emitting materials which emit three primary red, green, and blue colors has been made actively, and the intensive research has been made to improve their properties.
The material for organic EL devices has been proposed, for example, in Patent Literatures 1 to 6.